A secretive Washington firm that commissioned the dubious intelligence dossier on Donald Trump is stonewalling congressional investigators trying to learn more about its connections to the Democratic Party.

The Senate Judiciary Committee earlier this month threatened to subpoena the firm, Fusion GPS, after it refused to answer questions and provide records to the panel identifying who financed the error-ridden dossier, which was circulated during the election and has sparked much of the Russia scandal now engulfing the White House.

What is the company hiding? Fusion GPS describes itself as a “research and strategic intelligence firm” founded by “three former Wall Street Journal investigative reporters.” But congressional sources say it’s actually an opposition-research group for Democrats, and the founders, who are more political activists than journalists, have a pro-Hillary Clinton, anti-Trump agenda.